Difference Between While and Do While (With Table)

While and do while are loops used in the programming languages to perform several operations again and again until the condition mentioned inside it gets false. Both the loops are used for different purposes and are a very important part of any programming language. There are many differences between both of the types that help the programmers.

While vs Do While

The difference between while and do while loop is that the while loop first checks the condition and then gets executed only if the condition comes out to be satisfied, that is, if it turns out true, whereas the do while gets executed at least once before the condition is checked.

The while loop is a type of loop which is used to perform a certain set of statements again and again until the condition remains true. In this type of loop, the condition is checked prior to executing the statements, and thus, it is known as an entry-controlled loop as it controls when the iteration should flow.

The do while loop is a type of loop which is used to perform a certain set of statements again and again until the condition remains true, but in this type of loop, the statements get executed at least once a time prior to checking the condition and thus, it is known as an exit-controlled loop as it controls when the iteration process should stop.

Comparison Table Between While and Do While

Parameters of ComparisonWhileDo While
Syntaxwhile(condition){Statements; }do{ statements; } while(condition);
Condition controllingWritten at the start.Written at the end of the loop.
IterationsIteration does not flow until the condition is true.Iteration does flow at least once before checking the condition.
Alternate nameEntry-controlled loopExit-controlled loop
Use of semicolonNot usedIt is used at the end of the loop

What is While?

The while loop is a type of loop which is the most fundamental type used in the programming languages to perform a task again and again until the condition mentioned at the top of the loop remains true. The basic layout of syntax remains the same for all the languages, which look like the following: while (condition){ statements;}

In the syntax first, the while is written along with the condition for which the loop should work, which is written inside the parenthesis or round brackets. Then the set of statements are written inside the curly brackets, which are to be executed if the condition turns out to be true. It can be a single statement or a block of statements depending on the function needed to be executed.

The loop firsts check the condition whether it turns out true or false, if the condition happens to be true then the loop starts to iterate, and the statements written inside it gets executed. After that, the condition is checked again. This goes on until the condition does not happen to turn false. Once the condition becomes false, the inner statements are not executed anymore, and the iteration process stops meaning the loop is terminated, and the next immediate line of statements is executed.

What is Do While?

The do while loop is a type of loop that is used in the programming languages to perform a task again and again until the condition mentioned at the bottom of the loop remains true, but the specialty of do while is that the statements get executed at least once before it even checks the condition as the statements are written at the top, and the condition is written at the bottom. The basic layout of syntax remains the same for all the languages, which look like the following: do{ statements; } while(condition);

In the syntax, first, the do is written. Then the set of statements are written inside the curly brackets, which are to be executed if the condition turns out to be true. Then the while is written along with the condition for which the loop should work, which is written inside the parenthesis or round brackets. Then a semicolon at the end.

The loop firsts get executed and then checks the condition afterward whether it turns out true or false. If the condition happens to be true, then the loop starts to iterate again, and the statements written inside it get executed. After that, the condition is checked again. This goes on until the condition does not happen to turn false. Once the condition becomes false, the inner statements are not executed anymore, and the iteration process stops meaning the loop is terminated, and the next immediate line of statements is executed.

Main Differences Between While and Do While

  1. The syntax of the while loop looks like while(condition){ statements;} and on the other hand, the syntax for do while loop looks like do{statements;} while(condition);.
  2. The condition for which the loop should work is mentioned at the starting of the while loop, whereas the condition for do while loop should work is mentioned at the end of the do while loop.
  3. The iteration process does not take place until the condition mentioned in the while loop turns out to be true, whereas on the other hand, in the do while, the iteration process is executed at least one time before the condition written inside the while of do while loop is checked.
  4. The alternative name of the while loop is an entry-controlled loop as it can control the flow of the process from the starting, whereas the alternative name for do while loops are an exit-controlled loop as it controls when the loop should terminate.
  5. In the while loop, no semicolon is used in the syntax except in the statements, but the semicolon is used at the end of the while in the do while loop to terminate the iteration.

Conclusion

Both types of loops are used for iteration purposes and are used to achieve different goals. In contrast, the loop is used when it is definite that the loop should get executed only when the condition of the loop is satisfied or can say that it turns to be true. Whereas the do while loop is used when it is known that the loop should get executed at least once even if the condition later turns out to be false or can say before checking the condition mentioned inside while. If an individual wants the termination condition to be checked at the end, then do while loop is best; otherwise, use the while loop.

References

  1. https://dl.acm.org/doi/abs/10.1145/1460833.1460872
  2. https://link.springer.com/content/pdf/10.1007/BF00264291.pdf
  3. https://ieeexplore.ieee.org/abstract/document/6312840/
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